Hands-On ROS for Robotics Programming

Explaining configurable launch files using the <arg> tag

Arguments are a way to use variables in the scope of a launch file. Let's take the example of the world_name argument inside the include tag:

<include file="$(find gazebo_ros)/launch/empty_world.launch">    <arg name="world_name" value="$(find gazebo_basics)/worlds/gopigo.world"/>

This tag tells us which Gazebo world to use—referenced by the name attribute—and specifies the path where the file for the world can be found—that is, value="$(find gazebo_basics)/worlds/gopigo.world". Be aware that how you specify the file path is done in exactly the same way in which we tell it the launch file to include.

The syntax for the <arg> tag is neatly explained in the official documentation at http://wiki.ros.org/roslaunch/XML/arg ...